Treatment of aryl substituted mono-olefins



Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE TREATMENT or ARYL suns'rrru'riin MON-0LEFiN S No Drawing. Application March 17, 1938, Serial No. 196,540. In Great Britain April 1, 1937 3 Claims.

The present invention relates to the treatment of .aryl substituted mono-olefins and derivatives thereof and particularly to the treatment of mixtures of styrene and a-alkyl styrenes. In the 5 production of styrene, e. g. from isopropyl benzene, certain amounts of a-methyl styrene are always produced, and it is desirable for some purposes that the styrene should be freed from a-methyl styrene. 7 1o According to the present invention mixtures of styrene and a-alkyl styrenes are subjected to polymerisation conditions such that the a-alkyl styrenes are converted to polymers whereas the styrene remains unchanged. Particularly a mixture of styrene and a-alkyl styrenes is treated with sulphuric acid at about 70% to 90% strength at ordinary temperature so as to effect the polymerisation of the a-alkyl styrenes. Polymerisation may be eflected with or without the presence of a solvent or adiluent' such as isopropyl benzene. After treatment the unchanged styrene may be recovered from the polymerised substituted styrenes by any known means such as by steam distillation or distillation under reduced pressure.

The following examples illustrate the procedure for carrying out the invention and the results obtained:

Examplei A hydrocarbon mixture consisting of 26 per cent of styrene, 17 per cent of e-methylstyrene and the remaining percentage of isopropylbenzene was shaken with half its weight of sulphuric 5 acid 0! 70 per cent strength for 2 hours, the

temperature being maintained at about 20 C. by external cooling. The hydrocarbon product, after standing and separation of the aqueous acid layer, was washed successively with'water,

' then with aqueous alkali, and finally with water,

, and was then distilled under reduced pressure to yield:

I. A distillate containing 90% of the styrene originally present in the mixture as well as the isopropylbenzene and only a small amount of -metl:wlstyrene,' and II. A water-white oily residueconsisting mainly of lower polymers of a-methylstyrene.

Example 2 A hydrocarbon mixture consisting of 25 parts by weight of styrene, 25 parts of Jr-methyl styrene, and parts of isopropyl benzene was 5 treated with 10 parts by weight of sulphuric "used asplasticisers ior polystyrene.

is a reversible reaction the presence of thereaction product, methyl styrene, in the reacting 15 gases inhibits the formation of further methyl styrene, and more of the desired product styrene is produced according to the reaction.

However, a particularly important industrial 20 application for the said polymers is as plasticisers for co'umarone resins and styrene resins.

In the case of styrene resins it is known that polystyrene of itself possesses a low electrical 25 powerfactor rendering it very desirable as electrical insulating material but that it has thedrawback of being/brittle.

In order to overcome or minimise the objectionable brittleness of polystyrene it has been 30 proposed to' add plasticisers such 'as diphenyl phosphate, dibutyl phthalate, chlorinated naphthalenes and allcyl or aralkyl polynuclear hydrocarbons, but most plasticisers have the disadvantage of greatly raising the power factor of 35 the polystyrene.

The polymers of a-alkyl styrenes, however, as produced according to the present invention are free from the aforesaid disadvantage when For instance the polymer product of Example 1 above is a good plasticiser for hydrocarbon resins such as polystyrene and polyindene and has very good electrical insulating characteristics. For example the power factor of this polymer product-at 17 C. is as low as 0.0002 while even at C. the power factoris still quite low, namely 0.005.

What we claim'is:

1. The production of styrene-tree polymers of 5 3. A methodof separating styrene from mixtures containing styrene and a-alkyl styrenes which consists in subjecting said mixture to the selective polymerising action 01' 70-90% sulphuric acid at ordinary temperatures and thereafter separating the unchanged styrene from the polymerised a-allwl styrene.

HERBERT MUGGLE'I'ON STANLEY. JOHN BLAIR DYMOCK. 

